Severe back pain and nerve damage may be caused by injured, degraded, or diseased spinal joints and particularly, spinal discs. Current methods of treating these damaged spinal discs may include vertebral fusion, nucleus replacements, or motion preservation disc prostheses. Other treatment methods include spinal stabilization implants whereby a stabilization connector is secured to a pair of vertebral members spaced from one another. Some stabilization connectors are constructed to flex in a certain orientation or plane yet block or restrict movement in another plane. In this regard, determining the proper orientation of the connector relative to spinal joints greatly affects the effectiveness of the connector as a spinal stabilizer.
One exemplary connector is a spinal stabilization rod. Conventionally, these rods, which may be straight or pre-bent to have desired curvature, have a circular cross-section. The shape of the spinal stabilization rod has typically been applauded as allowing the surgeon a great degree of freedom in orientating the rod relative to a vertebral member. Notwithstanding this advantage, increasingly there is a desire for the rod to positionable at one of a number of discrete orientations. That is, stabilization rods can be constructed to provide a desired performance when placed in a specific orientation. It is difficult to achieve a specific orientation with conventional rods because the shape of conventional rods results in indefinitely defined possible orientations.
Moreover, a set screw is often used to secure the spinal stabilization rod in the rod-receiving channel of a receiver. The set screw typically has a planar surface that interfaces with the outer, and curved, surface of the stabilization rod. As a result, the set screw tangentially seats against the round stabilization rod. This tangential seating can result in focalized or poorly distributed contact forces.
Therefore, it would be desirable to have a spinal stabilization connector that presents discrete orientations at which the connector can be oriented. It would also be desirable to have a spinal stabilization connector that presents a relatively planar surface for engagement with the planar surface of a set screw used to secure the connector in a receiver so that contact forces are more effectively distributed.